Fasteners, such as nut and bolt assemblies, are used in a wide variety of devices. Use of such assemblies has achieved wide acceptance due to their high reliability and relatively low cost as compared to other fastening means. However, in some applications, such as liner assemblies on jet engine exhaust nozzles, the temperatures to which a fastener is exposed may exceed the fastener material's maximum allowable temperature, resulting in life reduction, or failure, of the fastener.
One solution to the problems posed by the high temperature environment would be to make such bolt assemblies using materials which inherently are able to withstand high temperatures with little or no detriment. However, present applications produce temperatures which are well above the maximum allowable temperature of most available materials from which bolt assemblies can be economically produced.
A more desirable solution to high temperature environments is to cool the bolt assembly so that the temperature of the bolt assembly material remains below the maximum allowable temperature thereof. Typically, such cooling is accomplished by circulating a coolant into contact with the bolt assembly, which coolant then absorbs heat from the bolt assembly. So long as the heat transfer rate from the bolt assembly to the coolant is no less than the heat transfer rate from the environment to the bolt assembly, the bolt assembly temperature can be effectively maintained below the maximum allowable temperature of the bolt assembly material.
In certain applications, such as liner assemblies on jet engine exhaust nozzles, the amount of coolant available is limited by engine performance considerations. Such liner assemblies may be secured to nozzle components by a plurality of bolt assemblies, each of which is cooled by the same coolant which has already been used to cool the liner assembly. Since the coolant temperature may rise dramatically as a result of cooling the liner assembly, the heat transfer rate from any given bolt assembly may not be sufficient to maintain that bolt assembly below its maximum allowable temperature.